In the welding industry, a tremendous number of robotic welding stations are operable to draw welding wire from a package as a continuous supply of wire to perform successive welding operations. The advent of this mass use of electric welding wire has created a need for large packages for containing and dispensing large quantities of welding wire. A common package is a drum where looped welding wire is deposited in the drum as a wire stack or coil of wire having a top surface with an outer cylindrical surface against the drum and an inner cylindrical surface defining a central bore that is coaxial to a central package axis. The central bore is often occupied by a cardboard cylindrical core, as shown in Cooper U.S. Pat. No. 5,819,934, extending about a core axis that is coaxial to the package axis. It is common practice for the drum to have an upper retainer ring that is used in transportation to stabilize the body of welding wire as it settles. This ring, as is shown in Cooper U.S. Pat. No. 5,819,934, remains on the top of the welding wire to push downward by its weight so the wire can be pulled from the body of wire between the core and the ring. In addition, a hold-down mechanism can be utilized to increase the downward force.
The welding wire in the package is in loops or convolutions wrapped about the package axis and forms the wire coil having a top and a bottom. The coil further includes radial inner and outer surfaces extending between the top and the bottom of the coil. As the welding wire is removed from the package, the wire is removed from the top coils or convolutions of wire wherein the top of the wire coil moves downwardly into the package. As a result, the top of the wire coil descends within the package and the outer and inner surfaces of the coil become shorter and shorter. Any braking device used in the packaging, which will be discussed in greater detail below, must then also be capable of descending within the package during the unwinding of the welding wire.
In order to work in connection with the wire feeder of the welder, the welding wire must be dispensed in a non-twisted, non-distorted and non-canted condition, which produces a more uniform weld without human attention. It is well known that wire has a tendency to seek a predetermined natural condition which, can adversely affect the welding process. Accordingly, the wire must be sufficiently controlled by the interaction between the welding wire package and the wire feeder. To help in this respect, the manufacturers of welding wire produce a wire having natural cast wherein, if a segment of the wire was laid on the floor, the natural shape of the wire would be essentially a straight line; however, in order to package large quantities of the wire, the wire is coiled into the package which can produce a significant amount of wire distortion and tangling as the wire is dispensed from the package. As a result, it is important to control the payout of the wire from the package in order to reduce twisting, tangling or canting of the welding wire. This condition is worsened with larger welding wire packages, which are favored in automated or semi-automated welding.
The payout portion of the welding wire package helps control the outflow of the welding wire from the package without introducing additional distortions in the welding wire to ensure the desired continuous smooth flow of welding wire. Both tangling or breaking of the welding wire can cause significant downtime while the damaged wire is removed and the wire is re-fed into the wire feeder. In this respect, when the welding wire is payed out of the welding wire package, it is important that the memory or natural cast of the wire be controlled, so that the wire does not tangle. The welding wire package comprises a coil of wire having many layers of wire convolutions laid from the bottom to the top of the package. These convolutions together form an inner diameter and an outer diameter wherein the inner diameter is substantially smaller than the width or outer diameter of the welding wire package. In this respect, the convolutions together form the radial inner and outer surfaces discussed above. The memory or natural cast of the wire causes a constant force in the convolutions of wire which is directed outwardly, such that the diameter of the convolutions is under the influence of force to widen. The walls of the wire welding package prevent such widening. However, when the welding wire is payed of the package, the walls of the package lose their influence on the wire, and the wire is forced toward its natural cast. This causes the portion of the wire which is being withdrawn from the package to loosen and tend to spring back into the package, thereby interfering with and possibly becoming tangled with other convolutions of wire. In addition to the natural cast, the wire can have a certain amount of twist, which causes the convolutions of welding wire in the coil to spring upwardly.
Payout devices, braking devices or retainer rings have been utilized to control the spring back and upward springing of the wire, along with controlling the payout of the wire. This is accomplished by positioning the payout or retainer ring on the top of the coil and forcing it downwardly against the natural springing effect of the welding wire. The downward force is either the result of the weight of the retainer ring or a separate force-producing member such as an elastic band connected between the retainer ring and the bottom of the package. Further, the optimal downward force during the shipment of the package is different than the optimal downward force for the payout of the welding wire. Accordingly, while elastic bands or other straps are utilized to maintain the position of the payout or retainer ring during shipping, the weight of the retainer ring can be used to maintain the position of the payout relative to the wire coils during the payout of the wire. However, the braking device must descend within the package as the wire in unwound from the wire coil. Further, the braking device must prevent the welding wire from springing up from the perimeter of the device which necessitates a close fit between the container and at least a portion of the braking device. As can be appreciated, imperfections in the container, coupled with a close fit between the container and the braking device, can cause the braking device to become lodged in the wire cavity, based on improper engagement with a container wall. This can be overcome by utilizing projecting lobes, as is shown in Cooper U.S. Pat. No. 5,819,934, or other container engaging projection, however, these can increase the cost of the packaging.
The welding wire can also be controlled by other mechanisms such as the packaged beads, as is shown in Chung. The packaged beads, along with pressing pipes, help control the out flowing welding wire as it exits the wire drum.
As can also be appreciated, the braking device can increase the overall cost and the shipping weight of the packaging. In order to provide a sufficient downward force, the braking devices used are made from dense materials such as different metals and plastics. Depending on the weight of the ring produced in a desired configuration, the braking device may need to have an increased thickness or a secondary weight source to produce a desired downward force to overcome the upward springing effect of the wire in the wire coil.
In order to prevent coil shifting during transportation of the container, the wire container often needs a separate hold down mechanism that can work in connection with the braking device to maintain the wire coil. The hold-down mechanism is typically an elastic member connected between the bottom of the container and a hold-down bar or member positioned above the braking device. The hold-down mechanism needs to be at least partially removed before the wire can be unwound from the coil for a welding operation.